An important phenomenon in cartography in the 19th Century is the emergence of thematic cartography and especially distribution maps. The latter represent the spatial distribution of a particular feature in an area. Distribution maps may be qualitative such as those representing the land use or land cover, geological maps, … or also quantitative, such as maps representing the population distribution by dots or isolines. Even if in the 18th C. (or even earlier), some thematic maps were drawn, the real development of the thematic mapping only started in the 19th C. In cartographic literature, large attention was paid to the cholera map of Snow from 1854. It has often been cited (also in geographical information science) as an example of early spatial analysis; what he visually did is today a well-known technique and methodology of buffer analysis in GIS. But the most impressive thematic maps are the early 19th C. chronostratigraphical maps, mostly described as geological maps. This type of inventory maps - important till the end of the 20th C. – are now completely substituted by digital data. If the development of thematical maps was an answer on one hand to industrialisation and changing ideas about the concept of richness, it was on the other hand also only made possible by the development of new printing techniques. Belgium was a forerunner in realizing geological maps. Already in the Dutch period (1815–1830) systematic field observations were executed in the southern part of Belgium. In this period a map was realized representing ore deposits (“Geologische kaart van een gedeelte der Nederlanden”), under the direction of J.E. Van Gorkum, with scientific input by professor Van Breda; the map was published in the Netherlands in 1834, after Belgian independency. The map is also interesting from another point of view as it is representing the triangulation network the Dutch established in Belgium before 1830 in the framework of the Military Reconnaissance. They were part of a systematic mapping project under ...